When a cutting work is to be effected on a narrow area located at a deep back side of an object to be worked, it is necessary to employ a tool chuck having a small outer diameter. Conventionally, as such chuck, a so-called hydraulic chuck designed to grip a cutting tool with use of a hydraulic pressure is employed. With this type of chuck, there is available only limited space for disposing required mechanisms such as a pressurization chamber and the gripping mechanism as a whole is formed compact. Accordingly, a cutting work at an area which is formed progressively narrower toward the back side can be carried out with ease. However, there is a need to feed an amount of coolant to the cutting portion, so a coolant feeding mechanism of various types would be employed, in addition to the chuck mechanism.
In the case of a hydraulic chuck disclosed in Patent Document 1, a pressurization chamber is formed between a sleeve which directly grips an inserted cutting tool and a body holding this sleeve. Then, with pressurization of a work oil reserved therein, an elastic deformable part formed at a portion of the sleeve is deformed to be reduced diametrically, thus gripping the cutting tool.
This hydraulic chuck has no arrangement for feeding coolant such as cutting oil agent to the cutting tool. Thus, for carrying out a cutting work on an object, coolant needs to be fed to the cutting tool with using a coolant feeding unit provided separately of the hydraulic chuck.
Further, in a hydraulic chuck disclosed in Patent Document 2, to a tip part of a body gripping a cutting tool, there is fixed a cover disc having a hole portion in which a shank portion projecting from the body of the cutting tool is to be inserted. This cover disc is not for gripping the cutting tool. Rather, in an inner circumferential face of the hole portion, there is formed a groove portion which extends along a longitudinal direction of the shank portion. This groove portion and the shank portion projecting from the body of the cutting tool together form a gap, through which coolant is discharged.